Vehicle fuel systems store and supply fuel used by an internal combustion engine. A typical vehicle fuel system includes a fuel tank, a pump operable for drawing fuel from the tank, and fuel lines interconnecting the various fuel handling components. A filter may also be included within the fuel system to remove any suspended particulate matter and other entrained contaminants prior to combustion of the fuel within the engine's cylinder chambers. A fuel regulator maintains sufficient pressure in the fuel lines, and also cycles excess fuel to the fuel tank.
In order to prevent fuel vapor from escaping into the surrounding atmosphere, vehicles may include equipment that isolates and stores vapor from the fuel tank, and that ultimately purges the stored vapor to the engine intakes. Certain vehicles, such as extended-range electric vehicles (EREV) or plug-in hybrid electric vehicles (PHEV), use sealed fuel systems to minimize the atmospheric discharge of hydrocarbon vapors, thus helping to minimize the vehicle's environmental impact. Sealing integrity is essential to the proper function of a sealed fuel system.